Pigment formulations and processes for their preparation

ABSTRACT

The present invention relates to a pigment formulation which comprises at least one organic pigment selected from C.I. Pigment Red 279 or C.I. Pigment Orange 80 (both thiazine indigo pigments) and at least one pigment-dispersing agent. The invention further relates to a process for preparing said formulation as well as to a method of pigmenting high molecular weight organic material of natural or synthetic origin with said formulation.

The present invention relates to novel pigment formulations havingimproved coloristic and Theological properties, to a process for theirpreparation and to their use for pigmenting high molecular weightmaterials.

Upon mixing and dispersing a pigment in a vehicle such as paint, gravureink or offset ink, it is generally difficult to stably disperse thepigment in the vehicle. Fine particles of the pigment, which have oncebeen dispersed in the vehicle, tend to floculate in the vehicle. Thisleads to an increase in the viscosity of the vehicle with the pigmentdispersed therein. Further, a reduction in the coloring power of an inkor paint malting use of the vehicle with the pigment dispersed thereinand a reduction in the gloss of a coating on the ink or paint can beobserved.

Thiazine-indigo pigments are a well known class of pigments. Theirpreparation is for example described in the published patent applicationWO 98/32800. Two pigments of this new class of pigments are ofparticular interest: C.I. Pigment Red 279 of formula (I) and C.I.Pigment Orange 80 of formula (II):

These two particular pigments provide very interesting properties, likevery high opacity and very bright coloration in paint applications.Nevertheless there is a need for improving the Theological properties ofthese two particular thiazine-indigo pigments.

Generally, pigment formulations are combinations or mixtures of pigmentswith pigment-dispersing agents. Pigment-dispersing agents are added topigments to facilitate dispersion in the application media, inparticular in paints or coatings, with the intention to improve theTheological and coloristic properties of the pigment formulations.

In U.S. Pat. No. 5,958,129 pigment formulations comprising a pigment ofthe perylene, perinone, quinacridone, azo, benzimidazolone,anthraquinone or anthranone type in combination with a structurallyanalogous pigment-dispersing agent are disclosed (see Col. 1, 1. 8-16).

The addition of structurally analogous pigment-dispersing agents allowsto reduce or to avoid floculation and to maintain a low viscosity of thepigment formulation even at high pigment concentrations. However, as thepigment-dispersing agent is selected due to structural analogy to thepigment, such dispersing agent is not universally applicable forstructurally different pigments. The selection of pigment-dispersingagents for improving the rheological and coloristic properties ofmixtures of organic pigments is thereby even more difficult.

Therefore the object of the invention is to provide pigment formulationswhich overcome the above described disadvantages of the prior art inrespect of coloristic properties, rheology and universal applicability.

It has been found that the object is surprisingly achieved by pigmentformulations which, in addition to the base pigment, C.I. Pigment Red279 or C.I. Pigment Orange 80, comprise one of the dirpersants offormula (III) or (IV) as defined below.

In contrast to the general approach known in the art, these twodispersant have a completly different structure compared to thethiazine-indigo pigments C.I. Pigment Red 279 and C.I. Pigment Orange80.

The invention therefore relates to pigment formulations comprising

-   a) at least one organic pigment selected from C.I. Pigment Red 279    of formula (I) or C.I. Pigment Orange 80 of formula (II) and-   b) at least one pigment-dispersing agent selected from pigment    dispersing agents of formula (II) or formula (IV).

The amount of pigment-dispersing agents (b) in the pigment formulationsaccording to the invention is not limited, as long as the requiredpigment quality is not adversely affected. In general a content of 0.5to 20% by weight, preferably of 1 to 10% by weight, ofpigment-dispersing agent, based on the total weight of the pigmentformulation, is appropriate.

In addition to pigment (a) and pigment-dispersing agent (b), the pigmentformulations according to the invention may also comprise furthercomponents, such as, for example, surface-active agents, resins,defoamers, anti-dusting agents, extenders or other customary additives.

Pigment formulations according to the present invention thereforepreferably comprise

-   a) 99.5 to 80% by weight of at least one organic pigment selected    from C.I. Pigment Red 279 of formula (I) or C.I. Pigment Orange 80    of formula (II),-   b) 0.5 to 20% by weight, preferably 1 to 10% by weight, of at least    one compound of the formula (III) or (IV),-   c) 0 to 10% by weight of surface-active agents and-   d) 0 to 10% by weight of customary additives.    The percentages are by weight and are based on the total weight of    the formulation.

Possible surface-active agents are customary anionic, cationic ornonionic surfactants, for example anionic substances, such as fatty acidtaurides, fatty acid N-methyltaurides, fatty acid isothionates,alklylbenzenesulfonates, alkylnaphthylenesulfonates, alkylphenolpolyglycol ether-sulfates and fatty alcohol polyglycol ether-sulfates;fatty acids, for example palmitic, stearic and oleic acid; soaps, forexample alkali metal salts of fatty acids, naphthenic acids and resinacids, for example abietic acid, and alkali-soluble resins, for examplecolophony-modified maleate resins; cationic substances, such asquaternary ammonium salts, fatty amine oxyethylates, fatty aminepolyglycol ethers and fatty amines; and nonionic substances, such asfatty alcohol polyglycol ethers, fatty alcohol polyglycol esters andalkylphenolpolyglycol ethers.

Examples of possible customary additives are defoamers, extenders,fillers, standardizing agents, preservatives, drying retardants andfoam-reducing agents.

The pigment formulations according to the invention can be both,mixtures of one or more organic pigments with in each case onepigment-dispersing agent, and mixtures of one organic pigment with oneor more pigment-dispersing agents.

The pigment formulations according to the invention are in generalfree-flowing powders or granules.

The invention further relates to a process for the preparation of apigment formulation according to the invention, which comprises addingthe pigment-dispersing agent to the organic pigment at any point of timeduring the entire preparation process.

The preparation process of an organic pigment generally comprises thefollowing steps: pigment synthesis, fine division, finishing, andisolation. The resulting product is either a press-cake or a dry powder.

The pigment-dispersing agents can be added before or during the pigmentsynthesis or before or during a fine division process or before orduring a solvent finishing. In all these steps temperatures of from 0 to200° C. may occur. The pigment-dispersing agent can of course also beadded in part portions at different steps of the process.

The essential step of the preparation process of an organic pigment isthe (chemical) pigment synthesis. All further steps are optional and areonly required if the resulting product of the previous step is to beimproved in its (physical) properties.

Typical fine division methods are for example grinding orreprecipitation. Addition of dispersing agent in the fine division stepis carried out, for example, in the course of dry grinding of the crudepigment, with or without additional grinding auxiliaries, on a roll orvibratory mill, or in the course of wet grinding of the crude pigment inan aqueous, aqueous-organic or organic grinding medium, for example on abead mill.

A typical finishing method is the so called solvent treatment or solventfinishing. The dispersing agent is therefore added in an aqueous,aqueous-alkaline, aqueous-organic or organic medium.

The pigment-dispersing agents can also be added to and incorporated intothe water-moist pigment press-cake before drying, in which case thepigment-dispersing agent itself can also be in the form of a press-cake.

It is furthermore possible to carry out dry mixing of pulverulentpigment-dispersing agents with the pigment powder.

The pigment-dispersing agents used according to the invention aresuitable for both, the use in solvent-containing and in aqueous systems.

The pigment formulations according to the present invention provide foroutstanding coloristic and rheological properties, in particular forhigh floculation stability, easy dispersibility, high gloss and a hightinctorial strength. The pigment formulations prepared according to theinvention can be employed for pigmenting (coloring) high molecularweight organic materials of natural or synthetic origin.

Examples of high molecular weight organic materials which can bepigmented with the pigment formulations mentioned are cellulose ethersand esters, such as ethylcellulose, nitrocellulose, cellulose acetate orcellulose butyrate, naturally occurring resins or synthetic resins, suchas addition polymerization resins or condensation resins, for exampleaminoplasts, in particular urea- and melamine-formaldehyde resins, alkydresins, acrylic resins, phenoplasts, polycarbonates, polyolefins, suchas polystyrene, polyvinyl chloride, polyethylene and polypropylene,polyacrylonitrile, polyacrylic acid esters, polyamides, polyurethanes orpolyesters, rubber, casein, silicone and silicone resins, individuallyor in mixtures.

The pigment formulations according to the invention are applicable tohigh molecular weight organic materials no matter if they are in theform of plastic compositions or melts or in the form of spinningsolutions, coatings, paints or printing inks. Depending on the intendeduse, it proves advantageous to use the pigment formulations obtainedaccording to the invention as a blend or in the form of preparations ordispersions. The pigment formulations according to the invention areemployed in an amount of preferably 0.1 to 10% by weight, based on thehigh molecular weight organic material to be pigmented.

In a further aspect of the invention it is also possible to add thepigment-dispersing agent to the pigment, or vice versa, directly in theuse medium. The invention therefore also relates to a pigmentpreparation essentially comprising said organic pigment, saidpigment-dispersing agent, said high molecular weight organic materialand, if appropriate, a surface-active agent and/or further customaryadditives. The total amount of organic pigment plus pigment-dispersingagent is preferably 1 to 10% by weight, based on the total weight of thepigment preparation.

EXAMPLES

In the following examples four pigment formulations according to theinvention and two pigment formulations without dispersing-agent wereprepared.

To evaluate the properties of the pigment formulations according to theinvention, an aromatic-containing alkyd melamine resin coating (AM)based on a medium-oil alkyd resin and a butanol-etherified melamineresin was selected out of the large number of known coatings.

Gloss measurements were made on cast films at an angle of 20° inaccordance with DIN 67530 (ASTMD 523) with the “multigloss” gloss meterfrom Byk-Mallinckrodt.

The gloss is considered the appropriate property to determine stabilityto floculation, as floculation reduces gloss. High gloss is therefore avalid indication for no or little floculation.

The parts are parts by weight and the percentages are percentages byweight of the substances thus described.

The following formulations were prepared:

Formulation 1

A pigment formulation is obtained by mechanical mixing of 243.75 partsof C.I. Pigment Red 279, of formula (1), with 6.25 parts of thepigment-dispersing agent of formula (III).

Formulation 2

A pigment formulation is obtained by mechanical mixing of 48.75 parts ofC.I. Pigment Red 279, of formula (I), with 1.25 parts of thepigment-dispersing agent of formula (III).

Formulation 3

A pigment formulation is obtained by mechanical mixing of 49.5 parts ofC.I. Pigment Orange 80, of formula (II), with 0.5 parts of thepigment-dispersing agent of formula (III).

Formulation 4

A pigment formulation is obtained by mechanical mixing of 48.75 parts ofC.I. Pigment Orange 80, of formula (II), with 1.25 parts of thepigment-dispersing agent of formula (III).

AM Coatings Prepared with Formulations 1-4

AM coatings of the formulations 1-4, were prepared (either drawn orpoured) and the gloss (as an indication for flocculation stability) ofeach was evaluated in comparaison to the basic pigment. Gloss drawnGloss poured Formulation 1 85 82 Formulation 2 71 60 P.R. 279 only 75 25Formulation 3 79 50 Formulation 4 83 73 P.O. 80 only 73 22

These results clearly demonstrate the improvement of the rheologicalproperties of AM paints when using pigment-dispersing agent of formula(I) or (IV) in pigment formulations comprising the thiazine-indigopigments of formula (I) or (II).

1. A pigment formulation comprising a) at least one organic pigmentselected from the group consisting of C.I. Pigment Red 279 of formula(I) and

 C.I. Pigment Orange 80 of formula (II)

and b) at least one pigment-dispersing agent selected from the groupconsisting of pigment-dispersing agents of formula (III) and of formula(IV).


2. A pigment formulation according to claim 1, comprising a) 99.5 to 80%by weight of the at least one organic pigment b) 0.5 to 20% by weight ofthe at least one pigment dispersing agent c) 0 to 10% by weight of atleast one surface-active agent and d) 0 to 10% by weight of at least onecustomary additive, based on the total weight of the formulation.
 3. Aprocess for the preparation of a pigment formulation according to claim1, comprising the steps of adding the at least one pigment-dispersingagent to the at least one organic pigment at any point of time duringthe preparation process of the at least one organic pigment.
 4. Theprocess of claim 3, wherein the at least one pigment-dispersing agent isadded before or during synthesis of the at least one organic pigment. 5.The process of claim 3, wherein the at least one pigment-dispersingagent is added before or during a fine division process on the at leastone organic pigment.
 6. The process of claim 3, wherein the at least onepigment-dispersing agent is added before, during or after a solventtreatment of the at least one organic pigment.
 7. The process of claim3, wherein the adding step further comprises mixing the at least onepigment-dispersing agent and the at least one organic pigment in theform of a water-moist press-cake.
 8. The process of claim 3, wherein theadding step further comprises mixing the at least one pigment-dispersingagent and the at least one organic pigment in the form of dry powders.9. A method of pigmenting high molecular weight organic material ofnatural or synthetic origin in the form of plastic formulations, melts,spinning solutions, coatings, paints, toners or printing inks,comprising the step of applying a pigment formulation as defined inclaim 1 to the organic material.
 10. A pigmented composition comprisinga) at least one organic pigment selected from the group consisting ofC.I. Pigment Red 279 of formula (I) and C.I. Pigment Orange 80 offormula (II), b) at least one pigment-dispersing agent selected from thegroup consisting of a pigment-dispersing agent of the formula (III) or(IV) and

c) a high molecular weight organic material of natural or syntheticorigin.
 11. The pigmented composition of claim 10, wherein the pigmentedcomposition is in the form of plastic formulations, melts, spinningsolutions, coatings, paints, toners or printing inks.
 12. A pigmentedcomposition colored by the pigment formulation according to claim
 1. 13.The pigmented composition according to claim 12, wherein the compositionis in the form of plastic formulations, melts, spinning solutions,coatings, paints, toners or printing inks.